Paving with polymer-bonded aggregates



Dec. 3, 1963 A. M. GESSLER ETAL PAVING WITH POLYMER-BONDED AGGREGATES Filed Aug. 3, 1959 FIG.-l

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FIG.- l2- Albert M. Ges s|er Inventors William J. Spdrks By $714M Patent Attorney 3,112,581 PAVING WETH PGLYMER-BONDED AGGREGATES Albert M. Gessler, Cranford, and William 3. Sparks, Westr'ield, NJ, assigaors to Ease Research and Engineering Company, a corporation of Delaware Filed Aug. 3, 1959, tier. No. 831,100 9 iaims. (Qi. 94-7) This invention relates to a novel type of paving construction and methods of preparing same, and more especially it relates to providing a simple method of coating any type of highway surface, e.g., macadam, asphalt-concrete, or Portland cement concrete, with a light-colored resilient surface coating which is not only water resistant but also resistant against softening by gasoline, jet fuels and lubricating oils.

Heretofore, asphalt roads have been used extensively because they provide lower cost construction than concrete highways designed for similar service, and yet have far greater durability and require less maintenance than the lower cost water-bound macadam roads. However, the black surface of asphalt roads is not as satisfactory as could be desired for certain purpose For instance, at night, particularly when wet, the driving visibility is not as good with asphalt surfaces as with other types which are not black. Published statements indicate that 5715 mile/ yr. more is required to light up asphalt roads than concrete. Also, asphalt surfaces are subject to an undesirable softening either under excessive heat alone, or when contacted with spillage of gasoline, jet fuels, lubricating oils and greases. Besides, upon aging, asphalt surfaces tend to slowly harden and crack due to oxidation and other weathering influences.

An object of the present invention is to overcome the disadvantages of such asphalt paving, while at the same time retaining a low-cost type of construction and also obtain a good resiliency in the paving surface, and providing resistance against softening due to heat or contact with oils.

Broadly, the invention comprises a paving construction having a surface layer of polymer-bonded aggregate, as, for instance, a fine sand having a coating of about 2 to 5% by wt. or" a polymer such as polyethylene of about 5,000 mol. wt.

Various types of polymers may be used for carrying out the invention, but generally any high mol. wt., i.e., molecular weight of at least about 1,000, thermoplastic linear or long-chain polymer having a softemng point of about 1l0230 F., preferably 120-215 F., and substantially free of cross-linking can be used, such as polyethylenes of relatively low mol. wt. (e.g. about 4,000 to 10,000) or medium mol. wt. (e.g., 15,000 to 30,000) or even high mol. wt. crystalline high-density polyethylenes having mol. wts. (e.g., 50,000 to 500,000) or more; also, polypropylenes of similar mol. wt. ranges, ethylene propylene copolymers, polyisobutylene, of low, medium or high mol. wts, styrene-isobutylene copolymers, polystyrene, polyvinyl chloride, polyvinylidene chloride, poly acrylates, etc., either alone or with plasticizing amounts, e.g., 1 to 40% or so, preferably 5 to 20% of elastomers, e.g., butyl rubber, hevea, GR-S, neoprene, diene-nitrile rubber, etc., or of lower mol. wt. plasticizers, e.g., mineral oils, fatty oils, waxes and natural or synthetic resins, e.g., cournarone-indene resins, low mol. Wt. styreneisobut lene resins, highstyrene-lowdiene resins, steamcraclted petroleum resins, etc. Polyolefin polymers have sharp melting points, such as low pressure (high density) polyethylene which melts at -275 F and polypropylene, which melts at 320-330 F. These linear polymers are all usable, with or without softeners or processing aids.

The aggregates to be used according to the invention 3,ll2,08l Patented Dec. 3., 1963 may be numerous conventional types or certain specially adapted types, as will be discussed further herebelow. For thin paving surface layers, e.g., about to /2" or so, a fine aggregate should be used, such as a sand having a grading of about 4" down to 200 mesh, or a finer sand ranging from 8 mesh to 200 mesh may be used; or even finer fractions may be used, such as 20 mesh to 200 mesh; and with any of these, some dust-type fillers may be used, such as ground limestone, pulverized sand, silicas, clays, etc. On the other hand, for coarser layers, e.g. from /2" to 5 or 6" in thickness, or for layers of similar thickness to be used as cushion layers to be coated with finer surface coating, large crushed aggregates may be used, such as crushed stone, gravel and air-cooled slag may be used having either a mixed grading of /2" to 3", or A" to 2" or /2" to 1', etc. alternatively, if a fairly thick layer, e.g., 2 to 6" or so is to be used Without any finer surface coating, the aggregate used may be a material of both coarse and fine aggregate and may include a dust filler, such as a mixture of 100 parts by wt. of coarse stone, parts by Wt. of sand, and 4 to 5 parts by wt. of powdered limestone. The above aggregates may be graded either for density and lowest voids, or for a controlled desired amount of voids.

If desired, the fine fillers to be used, e.g., crushed silica, clays, ground limestone, or even carbon black, etc., may be subjected to severe attrition, e.g., by ball-milling with steel balls, or roll-milling through tight set steel rolls, or stamping or any other severe attrition, prior to mixing with the polymer to be coated. It has been found that such severe attrition activates the surface of the filler particles at the places where the particles have been broken or otherwise attrited, and thereby provides a tighter bond when the polymer is subsequently coated thereon.

Various methods may be used in carrying out the present invention, depending upon various factors such as the particular type of polymer composition used, the type of aggregates used and according to the type of mixing equipment available. One technique, referred to as hot plastic mixing is to heat a polymer composition having a softening point within the range of about 120 to 212 F. and a melt viscosity (cps) of about 100 to 30,000 at mixing temperatures of ZOO-500 F, until it has softened to a hot fluid consistency, and then mix the aggregate into it, preferably gradually, until the final composition has about to 99% by wt. of aggregate and about 1 to 10, preferably about 2 to 8% by wt. of polymer. The preferred procedure here is to heat the aggregate, sand, a sand and stone, to 300500 F., and then to add the polymer binder, either as a flaked or pelleted solid at RT. or in melted form at some temperature close to that of the aggregate. This is the method used in the Pug Mill for mixing asphalt, the asphalt being added at about 300 F. to aggregate at 300350 F.

Thus, for example, a low-density polyethylene having an average mol. Wt. of about 5,000, which has a softening point of about 200 F. by Ring and Ball method (ASTM Standards D3626) may be heated to a temperature of about 300 to 400 F. and then a sand having a grading of about /4" down to 100 mesh, preheated to a similar temperature, is gradually added with con tinued mixing until the mixture contains about 96% by Wt. of sand and 4% of polyethylene and is substantially homogeneous. This mixture is then ready for application to a road surface where it is then compacted by rol ing or tamping or any other suitable method. Alternative polymer compositions may be used, such as one comprising a mixture of about 40 to 80% by wt. of high density polyethylene having an average mol. wt. of about 100,000, mixed with about 20 to 60% by wt. of polyisobutylene having a mol. wt. of about 3,000 to 20,000, alone or together with l to 10% by wt. of steam cracked petroleum resin. Another polymer composition which can be used comprises about 10 to 50% of polypropylene having an average mol. wt. of about 50,000 to 100,000, mixed with about 50 to 90% by wt. of polyethylene having an average mol. Wt. of about 1,000 to 10,000.

For paving surfaces not requiring oil-resistance, the polymer composition may comprise about 10 to 50% of polyisobutylene having an average Staudinger mol. Wt. of about 10,000 to 500,000, or a butyl rubber, e.g., made according to Patent 2,356,128, having a Staudinger mol. wt. of about 20,000 to 100,000, mixed with about 50 to 90% by wt. of steam-cracked petroleum resin, or other suitable plasticizers.

On the other hand, for compositions more especially intended for oil resistance, the polymer composition may comprise substantial proportions, e.g., to 50% or more of linear polymers containing substantial amounts of halogen, e.g., polyvinylchloride, polyvinylidene chloride, polytetrafiuoroethylene, polytrifiuorochloroethylene, neoprene, butadiene acrylonitrile rubber, styrene-acrylonitrile resin, styrene-vinylchloride resin, etc., or the more crystalline polyolefins mentioned hereinabove.

The paving construction may be of numerous different types, but generally should comprise a base course of crushed stone, gravel or slag or of granulated slag or cinders, etc., as a foundation layer on the road subgrade, although it is possible, if desired, to apply the polymer-bonded aggregate surface coating directly on the highway soil or subgrade. Preferably the paving construction comprises an intermediate layer such as a water-bound macadam or asphalt macadam (e.g., made by penetrating liquid asphalt down into a crushed coarse aggregate layer), or an asphalt concrete made by compacting into place a pre-mixed hot mixture of coarse aggregate and asphalt or other bituminous binder, or a Portland cement concrete layer.

Various other specific paving modifications may be used. For instance, a polymer-coated fine sand or ground limestone may be emulsified with Water and emulsifying agent, and then either applied by penetration down through a layer of coarse aggregate already in place in the roadway, or pre-mixed with the coarse aggregate and then placed in the roadway and then rolled.

Reinforcing, e.g., steel wire mesh, may be used, if desired, to strengthen relatively thick layers of polymerbonded aggregate made according to the present invention.

The paving surface compositions of this invention are also particularly adapted for repairing or patching holes or peck-marked surfaces of concrete highways or irregularities in the surfaces of any types of highways. They may be used for making a top coating over old asphalt road surfaces, or brick paving or concrete roads, especially those having bumps or irregularities in the surfaces.

An additional novel method of carrying out the pres ent invention is to first prepare a polymer-bonded fine aggregate, e.g., crushed sand or ground limestone, etc., of the desired composition, then sheet the resulting composition by calendering it into thin films or sheets having a thickness of about & to either in narrow strip form, e.g., for use as guide lines, or any types of highways or wide strips, e.g., 5 to ft. or more in width which can then be unrolled from a truck and laid directly on the highway surface and subsequently bonded into place by rolling with a heavy roller, with or Without the application of heat before or during the rolling.

Either for such particular application in the form of a self-supporting sheet or film, or for application in any other manner, various colored pigments may be used, such as white titanium dioxide or blue, red, yellow, etc., pigments or dyes or even carbon black in case it is desired to be a dark color While still retaining the oil-resistance properties of the polymer.

Oxidation inhibitors, and stabilizers against deterioration due to ultraviolet light may be added to the polymer compositions for use in this invention if desired. Suitable materials include alkylated phenols and bisphenols and thiophenols, amino phenols, aromatic amines and diamines, imines, etc., zinc and tellurium dithiocarbamates, sulfur, and other materials which are Well known in the rubber and plastics industry.

An alternative method of carrying out the invention, although only suitable for particular applications, is to cut back the polymer composition with a volatile solvent such as naphtha, kerosene, light petroleum oil, tetralin, petroleum aromatic solvents, etc. The resulting solution may be mixed with the desired coarse or fine aggregate prior to application to the roadway, or may be applied onto the aggregate which has already been placed in the roadway, but which has preferably been somewhat preheated before placing in the roadway. Such procedure has an advantage of permitting low temperature operation, but requires a delay in the curing or setting up of the polymer-bonding aggregate, to permit volatilization of the solvent.

A further modification of the invention is to press the polymer-bonded aggregate into large preformed slabs, e.g., about 4 ft. by 6 ft. to 10 ft. in size with a thickness of about 1 to 4" or so, or into bricks or blocks, patio blocks, fiagstone like slabs for walks, sidewalk pavements, cinder blocks, etc., or the polymer-bonded aggregate may be applied as a surface layer or coating on preformed slabs or bricks, etc. made of other materials such as asphalt, concrete, Portland cement concrete, clay bricks or even wooden blocks. In any case, these preformed articles are then positioned on the surface to be paved, preferably over a suitable foundation or base course of crushed stone, macadam, or concrete, and the spaces between them filled With a suitable grouting of hot thermoplastic sealant of polymer-bonded fine sand or ground limestone, and the entire road surface compacted by heavy rolling.

The various uses of the present invention include the paving of roads, streets and highways of all types, driveways leading in from roads to buildings or private homes, etc., or surface areas around stores, factories, gasoline filling stations, bus terminals, garages, airports, airport runways, decks of airplane carriers, etc. The invention is particularly useful for such purposes where it is desired to have a paving surface which is resistant to spillage of gasoline, jet fuels, or lubricating oils.

The invention will be better understood from a considerati-on of the above specification when read in conjunction with the accompanying drawing in which FIG- URE 1 shows a road pavement cross-section having a white polymer-bonded surface coating layer 1 immediately overlying an asphalt macadarn layer 2, which in turn rests on a crushed stone layer 3, placed directly on the subgrade 4.

The remaining FIGURES 2 to 20 show only cut-away portions of cross-sections of various types of paving con struction.

FIGURE 2 shows a thin polymer bonded surface coating 1 directly on a low-cost earth base 5.

FIGURE 3 shows a thick polymer-bonded surface layer containing both coarse and fine aggregate, supported on an earth foundation 5.

FIGURE 4 shows a better quality but more expensive paving construction in which the polymer-bonded surface coating 1 consisting of fine aggregate bonded with polymer is supported first on a water bound macadam layer 7, which in turn is supported by a crushed stone. base 3.

FIGURE 5 represents a construction similar to layers 7' and B of PEG. 4, but having a thick polymer-bonded. layer 6 containing coarse and fine aggregate.

FIGURE 6 is a further improvement over FIGURES substituted aliphatic-aromatic amides,.

4 and 5 in not only having the same crushed stone base layer 3 with the water bound macadam layer 7, containing both a thick polymer-bonded layer 6 containing coarse and fine aggregate but also containing a thin polymer-bonded fine aggregate surface layer 1 to completely seal the surface of the paving.

FIGURE 7 represents a paving construction somewhat analogous to F GURE 3, except that the polymer-bonded thick layer 6 is supported on a thick base 9' of granulated slag.

FIGURE 8 represents a construction in which a lower base course 3 of crushed stone supported on a polymerbonded macadam surface layer 10- made by penetratim an emulsion of fine polymer-bonded aggregate and water down into a layer of crushed coarse and fine stone.

FIGURE 9 illustrates a paving construction comprising a lower crushed stone base 3, and an overlying asphalt macadam layer 11 and a thin polymer-bonded surface coating 1. This FIGURE 9 corresponds essentially to the main features of FEGURE l.

FIGURE 10 is similar to FIGURE 9, except that the thin surface coating 1 is replaced by a thicker polymerbonded surface layer 6 containing both coarse and fine aggregate.

FIGURE ll represents a combination of FIGURES 9 and 10 in having both a thick polymer-bonded layer 6 containing both coarse and fine aggregate, as well as thin surface coating l of polymer-bonded fine aggregate.

FIGURE 12 shows a construction somewhat similar to that in FIGURE 9, except that the crushed stone base 3 supports an overlyin layer 12 consisting of asphalt concrete, i.e., premixed hot asphalt and coarse and fine aggregate, put in place and compacted by rolling, and then having a final overlying surface coating 1 of polymerbonded fine aggregate.

FIGURE 13 is analogous to FIGURE 12, but replacing the asphalt concrete layer 12 by a Portland cement concrete layer 13, but still having the finer thin surface coating 1 of polymer-bonded fine aggregate.

FIGURE 14 is analogous to FIGURE 13, except that in place of a thin polymer-bonded surface layer 1 containing only fine aggregate, this layer is replaced by a thick layer 6 of polymer-bonded coarse and fine aggregate.

FIGURE 15 represents a combination of FIGURES l3 and 14 in that the Portland cement concrete layer 13 is covered first with a thick polymer-bonded layer 6 containing both coarse and line aggregate and a thin surface coating 1 of polymer-bonded fine aggregate.

FIGURE =16 represents a superior but somewhat more expensive paving construction comprising a base course 3 of crushed stone with an overlying Portland cement concrete layer 13, then an asphalt-concrete cushion layer 12 a final thin surface coating layer 1 of polymerbonded fine aggregate.

FIGURE 17 shows a similar paving construction in winch a base course 3 of crushed stone supports only a single overlying thick layer 6 of polymer-bonded coarse and fine aggregate.

FIGURE 18 is similar to FIGURE 17 except that the polymer-bonded layer 6 is provided with steel wire mesh reinforcing 14.

FIGURE 19 represents a construction comprising a water bound macadarn base 7 supporting a brick layer 15 which has been coated over with a thin polymer-bonded surface coating 1.

FIGURE 20 shows a water bound macadam base 7 having a surface layer 15 of bricks imbedded in and grouted with polymer-bonded fine aggregate composition 16 between the bricks.

One method which has been found satisfactory for testing the strength and stability of paving constructions made according to the present invention is to make a Marshall stability test on small cylindrical samples of the thermoplastic polymer-bonded aggregate. The Man shall stability test is described in a pamphlet The Marshall Method for the Design and Control of Bituminous Paving Mixtures, published by the Marshall Consulting and Testing Laboratory. The test is made by preheating the sand or other aggregate to be used and also preheating the thermoplastic polymer to be used (in place of asphalt), mixing the two materials in the desired proportion, and while still hot tamping this mixture into a cylindrical mold whch is about 3 high and 4 in diameter. When cooled, the cylinder of polymer-bonded sand is removed from the mold and subjected to a load applied diametrically about the circumference, at a constant rate of 2" per minute, until failure or until maximum stress has been reached. The amount of deformation (in ths of an inch) at the time of failure or maximum load, is called the Marshall flow. The Marshall stability is expressed in lbs., and is usually made at a temperature of 140 F.

The various polymer-bonded aggregate compositions used in making various types of paving construction according to the present invention, generally have a Marshall stability (at 140 F.) of at least about 2,000 lbs., and preferably about 3,000 to 30,000. The corresponding Marshall flow generally ranges from about 4 to 25, preferably about 7 to 20. The Marshall stability/flow ratio (at 140 F.) is generally about 250- 3,000, preferably about 3002,000. In contrast, most asphalt compositions generally have a Marshall stability/ flow ratio (at 140 F.) substantially below 250, and usually between about 10 and 200. Asphalt paving compositions generally have a Marshall stability ranging from about 500 to 1500 or in some cases about 2,000.

In paving constructions, it is highly desirable that a pavement have a certain amount of flexibility as is the case with asphalt paving and with the polymer-bonded aggregate compositions used in the present invention, but it is also highly desirable that a pavement which has sufficient stability when hot (as in the sunshine at noon in summer) should not become too brittle during the cold Weather of Winter. Vice versa, it is desirable that a pavement which has good toughness characteristics when cold should not become excessively soft when hot. One method of ascertaining a merit rating of a pavement over the temperature range from cold to hot, is to determine the cold/hot Marshall stability ratio (e.g., F./140 F.). For asphalt paving compositions, this stability ratio is in the vicinity of 15, one test showing 16.3 in the case of an asphalt having an -100 penetration at 7 7 F. On the other hand, the polymerbonded aggregate compositions used according to the present invention generally have a corresponding cold/ hot Marshall stability ratio (75 F./ F.) of below 12, preferably about 1 to 10, and often as excellent as 1 to 5. Thus, the compositions used in the present invention can be designed for the desired strength and stability at the intermediate or average temperature, and then will be found to increase very little in brittleness at lower temperatures, but likewise will increase very little in softness at higher temperatures.

As a further indication of the great dilference and superiority of the present paving compositions compared to corresponding asphalt compositions, the 140 F. Marshall stability value divided by the softening point F.) gives a numerical value of at least 10, preferably 15 to 50 for the compositions of the present invention, compared to the range of about 2 to 5 in the case of asphalt compositions.

As further illustrations of the present invention, the following examples of paving construction are given:

Example 1 A 6.5 percent by Wt. of a polyethylene having an average mol. Wt. of about 5,000 was mixed with 93.5 percent by wt. of sand-stone aggregate (having a grading of about /2" down to 200 mesh) preheated to a temperature of about 450 F. and the resulting hot thermoplastic mixture was laid down as a surface layer on an asphalt road, and rolled to a /z" thickness, thus making an excellent oil-resistant, and light colored surfacing having both good visibility at night and also suitable for jet airplane runways.

This polyethylene-bonded sand composition showed a Marshall stability (at 140 F.) of 6,850 lbs., and a Marshall flow of 5.0, thus giving a 140 F. stability/flow ratio of 1,370, which is far above the range of about 10 to 200 for corresponding asphalt-sand compositions. As the melting point of this 5,000 mol. wt. polyethylene is about 200 F, the arithmetic value of the 140 F. Marshall stability divided by the melting point F.) is 34.2, which is far superior to the corresponding figure of 3.0 for a composition containing an 85100 penetration asphalt.

Example 2 A similar mixture of polyethylene aggregate was made, but supplemented with about 2% by wt. of titanium dioxide as white pigment. The resulting composition had excellent night visibility when used as a surfacing over an asphalt road.

Example 3 The polyethylene-bonded aggregate composition of Example 1 was also extruded while hot in the form of a curbing along the edge of a parking lot. It can similarly be used along t1 e edge of streets and highways.

Example 4 A steam-cracked petroleum resin having a softening point (Ring and Ball method) of about 212 F., an aver age mol. wt. of 1,100, a specific gravity of about 0.97, and a bromine number of about 8, was mixed in the proportions of about 6.5% with'a mixture of coarse and fine aggregate ranging from about /2" down to about 200 mesh, which had been preheated to about 450 F., and this mixture while hot and thermoplastic was rolled down as a surface layer about 1" thick on an asphalt road, thereby substantially improving the night visibility on the road. It was also extruded as curbing. This visibility was further greatly improved by the addition of several percent of titanium dioxide white pigment in the curbing. The curbing was clean white, and unlike Portland cement concrete, showed no discoloration when it was wet with water. The Marshall stability (at 140 F.) of the composition used in this example was about 15,000 lbs., and the Marshall flow was 15, thus making a 140 F. stability/flow ratio of 1,000 (which is exceedingly high compared to the range of about 10 to 200 for asphalt paving). The 140 F. stability divided by the softening point F.) was 70.7 (compared to only 3.0 for an asphalt of 85-100 penetration). Furthermore, the composition or this Example 4 had a very excellent cold/hot Marshall stability ratio (75 F./ 140 F.) of 1.3, which means exceedingly little change in strength and stability of such a composition over wide ranges in temperature. This is a tremendous superiority over corresponding asphalt compositions having a corresponding cold/hot stability ratio of about 16.3 for an asphalt of 85-100 penetration, which indicates undesirable softening at high road temperatures.

Example 5 The paving construction of Example 4 was given a,

surface coating of about 1" in thickness, consisting of the same steam-cracked petroleum resin plus a fine aggregate of sand (without any coarse aggregate) but containing an addition of 1% of titanium dioxide white pigment. This combination of both a tough flexible loadsupporting base and a flexible light colored surface coating produce a distinctly superior paving construction.

Example 6 Two parts by wt. of a steam-cracked petroleum resin having a softening point of about 158 F, and a specific gravity of about 0.96, were mixed with one part by wt. of a polyethylene of 5,000 mol. wt., by mixing the resin and the polymer in a large steam heated kettle at 300 F., and the resulting hot thermoplastic polymer blend was mixed in a concentration of 6.5% by wt. with coarse and fine aggregate in the following proportions:

/z" stone "parts by wt 180 stone do 450 Sand do 492 Polymer-resin binder doa. 78

After thorough hot mixing this paving composition was both tested for Marshall stability and also was laid down as a 1-inch layer on a roadway area and found to stand up well under heavy traific and show little loss in excellent properties with changes in temperature. It also had good oil resistance, and showed no softening whatsoever with spillages of gasoline, kerosene, or lubricating oil.

The Marshall stability (at 140 F.) of this composition was 3,600 lbs., and the corresponding Marshall fiow was 11.5. Thus, the 140 F. stability/flow ratio was 313, which is about twice as high as the 162 corresponding ratio for the plain steam-cracked petroleum resin if used without the addition of the polyethylene. This is an exceedingly important contribution to the art, because the steam-cracked petroleum resins are available commercially at relatively very low cost compared to the relatively expensive polyethylene, and yet the polyethyleneresin blend has a very light color and is subject to ready further improvement by the addition of titanium dioxide, and yet also gives oil-resistance.

The polymer-bonded aggregates and fillers are claimed as compositions per se in copending applications filed herewith.

It is not intended that this invention be limited to the specific examples which have been given merely for the sake of illustration, but only by the appended claims in which it is intended to claim all novelty inherent in the invention and all modifications coming within the scope and spirit of the invention.

What is claimed is:

1. A paving construction comprising a load-supporting base course and a surface course comprising to 99 wt. percent of aggregate bonded with 1 to 10 wt. percent of a substantially colorless thermoplastic polyolefin, substantially free of crosslinking, having an average molecular weight of at least about 1,000, a softening or melting point of between about and about 330 F. and selected from the group consisting of polyethylene, polypropylene, the copolymer of ethylene with propylene, polyisobutylene and m'mtures thereof.

2. A paving construction as in claim 1 wherein the polyolefin is polyethylene.

3. A paving construction as in claim 1 wherein the polyolefin is polypropylene.

4. A paving construction as in claim 1 wherein the surface course comprises both coarse and fine aggregate bonded with between about 2 and about 8 Wt. percent of polyolefin and in which said course has a Marshall stability value of at least about 3,000 lbs.

5. A paving construction as in claim 1 wherein the load-supporting base course comprises a water bound macadam course.

6. A paving construction as in claim 1 wherein the load-supporting base course comprises a Portland cement concrete course.

7. A paving construction as in claim 1 wherein the load-supporting base course comprises an asphalt-bonded aggregate course and the surface course comprises fine aggregate and white pigment.

8. A paving construction comprising a load-supporting base course and a surface course comprising 90 to 99 Wt.

percent of fine aggregate and white pigment bonded with 2 to 8 wt. percent of a polyethylene having an average molecular weight of between about 1,500 and about 10,000 and a softening or melting point of between about 120 and about 330 F.

9. A paving construction as in claim 8 wherein the white pigment is titanium dioxide.

References Cited in the file of this patent 10 Rowe Mar. 23, 1954 Wiese Aug. 23, 1955 Asaif Sept. 6, 1955 McKay Feb. 11, 1958 Heiges Mar. 25, 1958 Hardman Nov. 25, 1958 Welty Feb. 23, 1960 Bernier Dec. 13, 1960 FOREIGN PATENTS Great Britain 1939 Canada 1955 Australia 1956 

1. A PAVING CONSTRUCTION COMPRISING A LOAD-SUPPORTING BASE COURSE AND A SURFACE COURSE COMPRISING 90 TO 99 WT. PERCENT OF AGGREGATE BONDED WITH 1 TO 10 WT. PERCENT OF A SUBSTANTIALLY COLORLESS THERMOPLASTIC POLYOLEFIN, SUBSTANTIALLY FREE OF CROSSLINKING, HAVING AN AVERAGE MOLECULAR WEIGHT OF AT LEAST ABOUT 1,000, A SOFTENING OR MELTING 